Digital compact disc player security system reproducing method and apparatus

ABSTRACT

A security system for preventing disc players from being used with unauthorized software is disclosed. The security code is stored through modulating an offset of the physical position of a plurality of data bits from a nominal track position. A two part optical read head provides an RF signal corresponding to the presence of a physical offset modulation. The RF signal is present when there is a physical offset of the data bits defining a first logical state and the absence of the RF signal defines a second logical state. A digital security code is encoded and decoded in this manner. A system for encoding a security code through modulating the physical offset of a plurality of data bits from a nominal track position is also disclosed.

This is a divisional of prior copending application Ser. No. 08/555,835,filed Nov. 13, 1995, hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of computersoftware security systems, and, more particularly, the present inventionrelates to a digital compact disc player security system whereinsecurity code information is stored on a digital optical compact discthrough modulating an offset of the physical position of a plurality ofoptically encoded data bits on the disc from a nominal track position inorder to ensure that a disc player system is exclusively used withauthorized software containing a predetermined security code.

2. Description of the Related Art

Recently in the field of data storage and retrieval, the use of opticalcompact discs has grown significantly. Digital optical storage deviceshave the advantage of having a large storage capacity compared withother forms of data storage. In these systems it is often desirable toprotect a dedicated player system from being used with unauthorizedsoftware. This is especially true in the video game market where videogame manufacturers typically sell game playing devices at or near theircost with the expectation that sales and royalties on the software forthe games will provide a large return.

Conventional systems for protecting devices which are capable ofoperating with a variety of computer software typically employ asecurity code to protect the system from being used with unauthorizedcomputer software. In a conventional system for preventing a dedicateddisc reproducing apparatus from being used with unauthorized software,the system initially determines whether a security code is present at apredetermined memory location of the storage medium which contains thesoftware. The player or reproducing apparatus determines whether or notthe software is authorized by comparing the data stored in thepredetermined memory location with a security code. This is generallyknown as a security system or protect processing.

In recent years there has been a number of instances where even systemswhich have protect processing or security systems have been subject touse with unauthorized computer software. There have been instances wherethe protect processing has been illegally avoided even with the securitysystem as described above. One reason for this is that in conventionalsecurity systems the security code is located in a predetermined memorylocation which can be readily identified by examining the software. Thisis also at least partially due to the fact that the determination as towhether or not this recording medium is authorized and execution of thecomputer program are carried out by the same hardware. The presentinvention addresses these problems and overcomes the shortcomings of theprior art.

SUMMARY OF THE INVENTION

The present invention provides a digital optical compact disc recordingmedium which incorporates an improved system for storing and accessingthe security code to prevent copying of computer software from anunauthorized disc onto a dedicated disc player. In order to solve theabove-mentioned problems, a digital optical compact disc according tothe present invention incorporates a security code which is defined bymodulation of a physical offset in the radial direction or “wobbling” ofthe position of a plurality of data bits from a nominal track position.The physical offset modulation is digitally encoded to define a securitycode.

The security verification method according to the present inventioncomprises the steps of reading out the modulated physical offset orwobbling of the data bits in the radial direction of the recordingmedium so that the security code can be detected. The detection step ofdetecting the certification data or security code is followed by adiscrimination step of determining whether or not the certification datawhich is detected corresponds with a security code previously set inadvance. It should be noted that when it is determined during thediscrimination step that certification data and the security code set inadvance do not match each other, the system inhibits further processingof the disc software, thus preventing unauthorized software from beingused with the system.

Additionally, the above mentioned disc recording and reproducing methodincludes the step of displaying video information identifying the gamemanufacturer as the licensor or creator of the software. This occursonly when the certification data corresponds with or matches thesecurity code. In the preferred embodiment of the present invention,this occurs after a second check or verification which ensures that thedisc contains a proprietary video image or message at predeterminedlocations of the disc. By incorporating this step into the process ofreading the software from the disc, the game manufacturer is able toforce anyone who makes unauthorized software for use with the system toviolate the copyright or trademark laws. This occurs because the systemwill automatically display a proprietary screen identifying the gamestation manufacturer as the creator or licensor of the software. If thesoftware is unauthorized, its creator will automatically be in violationof the trademark laws because the software is not actually authorized orlicensed as stated by the display screen.

In order to solve the problems mentioned above, the improved system ofthe present invention incorporates a means for reading the modulatedphysical offset or wobbling of the position of a plurality of the databits on the disc. The physical position of the bits is modulated in theradial direction to define a security code. The security code thereforedoes not reside in a predetermined memory location but rather isembedded in a general area of the disc by modulating the location of thedata bits with respect to a nominal track position. This is advantageousbecause a person examining the software would be unable to determine thesecurity code. In the preferred embodiment, the presence of the physicaloffset or modulating is defined to be a logical “1” and the absence ofwobbling is defined to be logical “0”.

A detecting means for detecting certification data which has been storedby modulating the physical position of a plurality of data bitsdetermines the security code. In the preferred embodiment, the opticalread head is divided in two parts in order to determine whether thesecurity code is present. Data bits which are offset from a nominaltrack location can be detected with such a device. The main datacomprising the software for the computer game stored on the disc is alsoread out with the same read head.

In the preferred embodiment of the present invention, the systemperforms an initial check to determine whether or not the disc containsa “wobbled” code in the TOC (Table of Contents) area of the disc. In anauthorized disc, the security code is repeated several times in order toensure that it is properly detected without the need to add errorcorrection bits to the security code. The system initially checks todetermine whether the disc contains wobbling of the data in the TOC areaof the disc before actually checking the actual code. If the disc doesnot contain a wobbled code, the system then determines if the disc isactually an audio disc. If it is an audio disc the system proceeds toplay the audio disc and provide an audio output. If it is not an audiodisc then the system shuts down.

If the disc does contain a “wobbled” code in the TOC area of the disc,the player proceeds to decode the wobbled code and transmit this decodeddata to a mechanical controller. If the wobbled code matches apredetermined security code, then the system performs a second check onthe disc for verifying authenticity. If the wobbled code does not match,the player then checks to see if the disc is an audio disc as notedabove. If the disc passes the first code verification, the disc playerthen proceeds to verify that the disc contains a logo which matches alogo stored in the system. This second verification is performed toverify that the disc is actually authorized.

A preferred embodiment of the disc player security system of the presentinvention is described in detail below with reference to the attacheddrawings. Although the preferred embodiment is described with referenceto a video game player system it is recognized that this is exemplaryonly and that other alternate applications are also anticipated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of an exemplary embodiment of thesecurity system of the present invention;

FIG. 2A illustrates the typical physical relationship of data bitsstored in a track on a digital optical disc;

FIG. 2B illustrates the physical offset modulation or wobbling or thedata bits from a nominal track position according to the presentinvention;

FIG. 3 illustrates decoding of the modulated output based on a physical“wobbling” of the data bits which defines digital data.

FIG. 4 illustrates a block diagram of an exemplary optical decoder foruse with the present invention;

FIG. 5 illustrates a flow chart explaining operation of the disc playersecurity system of the present invention;

FIG. 6 illustrates an exemplary video display output which is to bedisplayed after it is determined that the disc has proprietary logoinformation stored in predetermined memory locations; and

FIG. 7 illustrates a system for encoding a security code on a digitaloptical disc through offsetting the physical position of a plurality ofdata bits from a nominal track position in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the disc reproducing apparatus according tothe present invention is set forth below with reference to the drawings.In this preferred embodiment, a video game device employs the securitysystem to prevent unauthorized use of a machine with software containedon a digital compact disc. A digital optical compact disc which embodiesthe present invention has its main or primary data recorded in aconventional manner via EFM (Eight to Fourteen modulation) in NRZ (NonReturn to Zero) format. This information resides in the normal track andsector locations on the disc. This is similar to the manner in whichconventional audio compact discs are encoded. In the preferredembodiment of the present invention, the data bits which define the TOC(Table of Contents) area of the disc are stored such that a wobbledsecurity code is embedded in the TOC track as a modulation of a physicalpositional offset from a nominal track location. The security code isstored by a process in which a 22.05 kHz signal is used as themodulation carrier wave which is digitally modulated in NRZ (Non Returnto Zero) format to encode the security code. The positional offset whichdefines the security code is a physical offset in the radial directionof the optical disc. The frequency of the offset is based on the linearvelocity of the optical head passing over the track and the resultantreproduction of the offset as an RF signal. It should be noted that the22.05 kHz signal is a signal having a frequency which is one-half of thesampling frequency of the digital optical compact disc. (44.1 kHz) Thisallows accurate reproduction of the offset or wobbling signal. The TOCportion of the disc thus has two forms of information stored in thisarea. First, the TOC may have information digitally encoded and definedas the pits and holes that make up the TOC track. Additionally, thesecurity code is stored through a modulation of a positional offset ofthe data bits from a nominal track position.

The security code which is stored in the TOC area of a digital opticalcompact disc in accordance with the present invention thus does notreside in a specific or predetermined track and sector location on thedigital optical compact disc. The security code data is typically onlyseveral bytes in length. In the preferred embodiment of the presentinvention, because the security code is not stored in a specificaddressable location, it is more difficult for a person examining thesoftware to copy the security code. The code is repeatedly encoded inthe TOC area of the disc so that the optical pick-up 2 and security codedetector are more likely to correctly identify the presence of thesecurity code.

FIG. 1 illustrates a block diagram of the system used for decoding asecurity code in accordance with the present invention. In thisillustration an optical pick up 2 generates a signal by reading thepositional fluctuation of data bits on the disc 1 in the radialdirection with respect to a nominal track position. This is consideredto be “wobbled” data. Although a single pick-up head generates both thesecurity code and the primary data stored on the disc, two separatehardware sections in the game player process these signals.

A security code detecting section 3 detects the presence of securitycode based on the so-called “wobbled” data. A disc reproduction controlsection 4 correlates the security code with a predetermined code storedin the system's memory to determine whether or not the disc is anauthorized disc. A main data demodulation section 5 reads out theprimary or main data stored on the compact disc for use with the discplayer machine. This main data is either the software for a video gameor it may alternatively be audio information defining a sound recording.The main data demodulating section 5 feeds a main data buffer 6 havingan output which in turn also feeds an interface section 7. The programexecution control section 8 controls execution of the software containedon the disc. Display of video information is produced by the display 10.The display is controlled by the display control section 11. The display10 displays the game information after successful completion of thesecurity code verification. In the preferred embodiment of the presentinvention, the system also performs a second check to verify that thedisc is authentic. This second check verifies that a logo stored in apredetermined location on the compact disc matches a logo stored on themachine. If an audio disc has been inserted into the player, the systemwill provide an audio signal output from terminal 9.

FIG. 2A is a greatly enlarged view which illustrates data bits stored ona typical conventional digital optical disc. For the sake ofillustration, the data bits are shown in a linear arrangement, however,those skilled in the art will appreciate that the data bits are actuallyarranged on a conventional disc in a slightly curved pattern to matchthe curvature of the tracks on the disk. This is also true of digitaloptical discs which embody the present invention. FIG. 2B illustratesthe presence of a wobbled code wherein the physical position of theinformation bits on the disc are modulated as an offset from a nominaltrack position to provide a modulated signal which, in the preferredembodiment, is a security code for the disc. The positional offset ofthe data bits from a nominal track location is in the radial directionof the recording medium. In the preferred embodiment of the presentinvention the security code is located in the Table of Contents (TOC)area of the disc, however, it is contemplated that other track locationson the disc are equally suitable.

Because the security code is stored numerous times in the TOC area ofthe disc, the security code can be more reliably reproduced without theneed for storing additional error correction bits. The disc player isthus more likely to reproduce the security code accurately if there is ascratch or dust on the disc. Storing the security code numerous times inthe TOC area of the disc allows the security code to be stored withoutalso storing additional error correction bits.

FIG. 3 illustrates an example of the resultant digital output from thesecurity code detecting section wherein the presence of wobbling or thephysical offset of the data bits from the nominal track positionindicates a logical “0” and the lack of wobbling or lack of offset froma nominal track position is indicated as a logical “1”. In the preferredembodiment the security code is stored in NRZ (Non return to zero)format. It is understood, however, that alternate schemes for encodingthe security code are also possible. In the preferred embodiment thefrequency of the offset for the security code is 22.05 kHz which is onehalf of the sampling frequency of conventional optical compact discs. Asseen in the illustration of FIG. 3, the security code is digitallyencoded through the presence and absence of a physical offset of thedata bits which, when present, is at a frequency of 22.05 kHz. Thesecurity code is repeatedly stored in the TOC area of the disc severaltimes as noted.

FIG. 4 illustrates an optical signal decoder and corresponding decodinghardware for use with the present invention. The optical detector 13 iscomprised of a two part photodetector which is divided into two halvesthat are positioned above a nominal track position on the disc. The twopart photodetector 13 provides one pair of output signals. The pair ofoutput signals is applied to two corresponding inputs of a differentialamplifier 15. The differential amplifier has its output connected to theinput of a low pass filter 17 which has its output connected to theinput of the tracking servo 18. The tracking servo 18 performspositional control of the optical detector 13.

The output of the differential amplifier 15 which is considered to be anRF signal also feeds an input of a 22.05 kHz band pass filter 20. Theoutput of the 22.05 kHz band pass filter 20 feeds the input of a peakhold circuit 21. The output of the peak hold is applied to the input ofa comparator 22. The peak hold circuit 21 provides a digital outputcomprising the signal decoded by examining the TOC track for thepresence of “wobbling” or the offset of the data bits from a nominaltrack position. Because the photodetector 13 is divided into twoseparate areas, the difference of the two signals generated by the twophotodetector areas, identifies the presence of a wobbling or securitycode which in the preferred embodiment has a frequency of 22.05 kHz. Asshown in FIGS. 2 and 3, it is not the actual physical offset of a singledata bit which defines a particular bit of the security code, but rathereach bit of the security code is defined as the presence or absence ofwobbling over a brief period of time. The comparator 22 makes adetermination as to whether the disc is authentic based on whether thesecurity code matches a code previously stored in the memory of the discplayer. The output of the comparator 22 feeds the input of the disccontroller 24.

The pair of outputs from the two pair photodetector 13 also feeds thetwo inputs of an adder 26. The adder 26 provides a digital output whichconsists of the main or primary data stored on the disc. This is thedata which is determined by the pits and holes on the disc. An outputfrom the adder 26 feeds an amplifier 27 which has an output which isconnected to an input of a signal processor 30 for processing theprimary data stored on the disc.

A flow chart for explaining the operation of a preferred embodiment ofthe disc reproducing apparatus is shown in FIG. 5. The security codedetecting section 3 of FIG. 1 initially determines whether a 22.05 kHzsignal is present as an RF signal generated by the optical pick-up head.This is based on the output from the optical detector 13. If there iswobbling of the data on the disc, the optical detector 13 will providean RF signal which corresponds to the frequency of the positional offsetof the data bits from a nominal track position. In the preferredembodiment of the present invention this is a 22.05 kHz signal. Thisstep is identified as step S1 in the flow diagram of FIG. 5. If it isdetermined such an RF signal exists as an output from the opticaldetector, then in step S2, it is determined whether or not the 22.05 kHzsignal is in an a.c. state. The determination of whether the 22.05 kHzsignal is in an a.c. state is not a determination of whether there is aperiodic waveform, but rather this is a determination of whether thewobbled signal changes logical states frequently as identified in FIG.3. This first check will exclude discs from use on the machine which dohave wobbling of the data bits in the TOC track but which do not havethe wobbled track modulated to define a digital signal.

If it is determined that the 22.05 kHz signal is in an a.c. state,predetermined demodulation processing in which the 22.05 kHz signal isconsidered the carrier is performed on the RF signal generated by theoptical pick-up in step S3. This is the detection of the security codewith the system set forth in FIG. 4. The security code stored on thedisc is thereby determined. The security code is then sent to thereproduction control section 4 as shown in FIG. 1. Also if it isdetermined that the optical pick-up has not generated a 22.05 kHz signalor if it is determined to be in a d.c. state (no wobbling or offset), asignal indicating that the a.c. signal does not exist is sent to thereproduction control section 4.

The disc reproduction control section 4 determines whether the securitycode stored on the disc and the security code stored on the game or discreproduction device match or correspond with each other. This occurs instep S4. This determines whether the disc is an authorized disc for thesystem.

In the system of the present invention, if the disc passes the securitycode matching which compares the security code stored on the playermachine with the wobbled code stored on the disc, the system thenperforms a second verification. In step S5, the system reads out a logoand/or license data from the disc in order to perform the secondverification. The second verification is performed in step S6 whereinthe system compares a logo and/or license data stored in memory of themachine with the contents of predetermined memory or storage locationson the disc. This second verification also determines whether the discis authentic.

Step S7 of FIG. 5 is a step wherein the system will display a visualimage identifying the software as being produced or licensed by the gamemanufacturer. This would force someone who illegally copies the securitycode to violate the trademark laws because the system would identify thesoftware as being licensed when it is actually not licensed. In thepreferred embodiment of the present invention, a logo stored in a memoryassociated with the player machine is compared with a logo stored in apredetermined memory location on the disc. This occurs in step S6. Thesystem passes control to the software contained on the disc only if thetwo logos or images match. The system ceases operation if the two logosdo not match. This second verification is performed to increase thelikelihood of eliminating unauthorized discs from use on the machine. Ifthere is a match, the system will then display the proprietary visualimage in step S7. This is described further below.

If it is determined through the two verifications that the disc isauthentic, a control signal is generated to instruct that main datatransfer occur and that control be passed to the software stored on thedisc. The program execution control section B illustrated in FIG. 1sends a signal to the interface section 7 so that the software stored onthe disc can be transferred onto the system memory in order to transfercontrol to this software. This occurs in step S8 of the flow diagramillustrated in FIG. 5. Step S8 which is execution of the disc contentwill not occur unless the disc also passes the second verification ofstep S6.

On the other hand, if the security code does not match, or if the 22.05kHz signal does not exist or if the 22.05 kHz signal is not in an A.C.state, or if the logo does not match the logo on the disc, it is thendetermined whether the disc is merely an audio disc. This is step S9 inthe flow diagram of FIG. 5. If the disc is an audio disc, the systemwill allow the disc to be played on the unit because it is moredesirable that a game device have this alternate capability. The systemthen outputs an audio signal as identified in step S10 of the flowdiagram of FIG. 5. Alternatively, in step S11, if it is determined thatthe disc is not an audio disc, the system will stop reproduction of thedata from the disc and control will not pass to the software on thedisc.

FIG. 6 illustrates an exemplary proprietary display which may be used toeliminate disc counterfeiters. The display may include one or more ofthe visual indicators identified on the screen 50. A registeredtrademark 51 may be used to force a counterfeiter to violate thetrademark laws. Alternatively, an image identifying the software asbeing licensed by the machine manufacturer may also be used as indicatedby block 52. A company name may also be used as indicated by block 53.All of these additional items may be used together or only select onesmay be used. These visual indications can be stored in a memory of thesystem and compared with the contents of specific memory locations onthe disc in accordance with the second check or verification identifiedabove. This second verification is identified as step S6 in the flowdiagram of FIG. 5. Alternately, a simple code matching may be used tofurther verify that the disc is authorized. For example, an ASCII codestored in a memory associated with the machine may be compared with thecontents of predetermined storage locations on the disc.

FIG. 7 illustrates a system for encoding the wobbled security code ofthe present invention on a digital optical compact disc. Pre-Mastered CD31 (PMCD) is a master disc having a game program, game data andidentification data which identifies the type of the disc storedthereon. The identification data is recorded in a predetermined area ofthe master disc. The identification data indicates whether the masterdisc is to be used with a particular game playing device andidentification of which country or area of the game is to be used. Forexample, this information could be Game X—Master Disc—“Japan”. Thepick-up 33 reads the digitally encoded information from the master disc31. The detector 34 detects the identification data and the controller25 transfers the identification to the security code generator 37 if themaster disc is identified as being authentic. If the identification datais not detected, the cutting machine operates only as a conventionalcutting machine for a compact disc and will not insert a wobbled code.

The security code generator 37 generates a binary security code whichdepends on the particular country in which the disc is to be sold. Forexample, the following codes could be used:

Master Disc—Japan=ABCD

Master Disc—USA=EFGH

Master Disc—Europe=WXYZ

The AOD (Acoustic Optic Deflection circuit) drive amplifier 38 amplifiesa signal generated by the security code generator 37. The AOD deflectioncircuit 39 receives an output from the AOD drive amplifier and outputsan RF signal which modulates the physical position of the laser beamwith respect to a nominal track position depending on the security codewhich is supplied from the security code generator 37 in accordance withthe coding scheme identified above. For example, the presence of anoffset may indicate a logical “1” or first logical condition and theabsence of wobbling may indicate a logical “0” or second logical state.The AOD drive 39 is the element which moves the laser in the radialdirection off of a nominal track position location for encoding the pitson the CD. The pits on the CD are thus wobbled in response to the RFsignal output from the AOD drive amp 39. The physical placement of thepits on the disc is thus modulated from a nominal track position inorder to define the security code. The EFM unit 40 encodes the gameprogram and game data as a 14-bit word based on an original 8 bit word.This is known as Eight-to-Fourteen Modulation (EFM). The recording laser42 provides a signal which cuts the pits on the master disc 45 in aconventional manner after reflection by a mirror 43 and passing througha lens 44. The signal output from the laser 42 is positionallycontrolled via the AOD 39.

The present invention is subject to many variations modifications andchanges in detail. It is intended that all matter described throughoutthe specification an shown in the accompanying drawings be consideredillustrative only. Accordingly, it is intended that the invention belimited only by the spirit and scope of the appended claims.

We claim as our invention:
 1. A device for reading digitally encodeddata comprising: first and second optical receivers positioned above anominal track position on a recording medium and receiving opticalreflections from the recording medium to produce corresponding signals,respectively; and a device for comparing the signals received from thefirst and second optical receivers for identifying a physical offsetmodulation of a plurality of data bits from the nominal track position.2. The device for reading digitally encoded data of claim 1, wherein thedevice for comparing identifies the offset of the data bits from thenominal track position as one of a logical “0” and a logical “1”.
 3. Thedevice for reading digitally encoded data of claim 2, wherein the devicefor comparing identifies the lack of the offset of the data bits fromthe nominal track position as the other of the logical “0” and thelogical “1”.
 4. The device for reading digitally encoded data of claim3, wherein a code of a given number of bits is formed such that each bitof the code is represented by one of the logical “0” and the logical“1”, and wherein the device for comparing further compares the code witha predetermined security code.
 5. A method for decoding digital datacomprising: generating first and second signals based on opticalreflections from opposite sides of a nominal track position on arecording medium; comparing the first and second signals to identify aphysical offset modulation of a plurality of data bits from the nominaltrack position; and generating a code determined by the offsetmodulation of a plurality of data bits from the nominal track position.6. The method for decoding digital data of claim 5, comprisingidentifying the offset of the data bits from the nominal track positionas one of a logical “0” and a logical “1”.
 7. The method for decodingdigital data of claim 6, comprising identifying the lack of the offsetof the data bits from the nominal track position as the other of thelogical “0” and the logical “1”.
 8. The method for decoding digital dataof claim 7, wherein the code has a given number of bits each of which isrepresented by one of the logical “0” and the logical “1”, and whereinthe method further comprises comparing the code with a predeterminedsecurity code.